JPH10210004A - Cdma mobile communication system and transmission/ reception equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the time of code synchronous detection of spectrum spread and to prevent the degradation of synchronous detection characteristics in a CDMA mobile communication system. SOLUTION: On the transmission side, first, second,..., N-th spread codes are used for (a+1)th, (a+2)th,... (a+N)th symbols ((a) is an arbitrary integer) of information modulation symbols on the transmission side to perform spectrum spread and transmission. On the reception side, matched filters 22 to 24 matched to first,..., N-th spread codes are used to obtain a correlation waveform from a reception signal. A delay circuit 25 is used to delay this correlation waveform by 0 to N-1 information modulation symbols times, and the sequence of peak detection of correlation is detected to perform discrimination of a base station and detection of code synchronization. Thus, the time of code synchronous detection is shortened and the degradation of synchronous characteristics is prevented in comparison with the use of a sliding correlator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to code division multiple access (CDMA) using spread spectrum communication.
n Multiple Access) Mobile communication system and CDM
A transmission / reception device.

[0002]

[Prior Art] US USTelecommunications Industry
Association / Electronic Industries Association
2. Description of the Related Art A CDMA mobile communication system using a long-period spreading code represented by IS-95 (TIA / EIA) standard as a pilot is known.

FIG. 7 is a diagram showing the timing of codes in the conventional CDMA mobile communication system. Referring to FIG. The following describes how to spread the spectrum of an information modulation symbol. In FIG. 7, reference numeral 1 denotes an information modulation symbol, and reference numeral 2 denotes a spreading code (called short PN in the standard) used for spread spectrum. In this figure, for the sake of simplicity, in the traffic channel of the above-mentioned conventional method, there is a terminal-specific offset, which is used for terminal identification and scrambling.
The description of the ng code and the orthogonal code for orthogonal multiplexing is omitted.

As shown in FIG. 7, in this conventional system, 2 ¹⁵ = 32768 chips are used as a spreading code (short PN).
PN code having a long cycle is used, and the spectrum is spread by multiplying 128 chips in one cycle by one information modulation symbol. That is, the first symbol of the information modulation symbol is multiplied by the first to 128th chips in one cycle of the spread code to spread the spectrum, and the second symbol is the 129 to 25th of the spread code.
Spread spectrum is performed by multiplying 6 chips, and in the same manner, 32641-th in the spread code at the 256th symbol
Spread spectrum is performed by multiplying 32768 chips. Then, the 257th information modulation symbol is multiplied again by the first to 128th chips in the spread code, and the subsequent information modulation symbols are similarly spectrumd by sequentially using a part (128 chips) of the spread code. Is spreading. As a result, the processing gain of the spread spectrum becomes 128 times.

In general, when spreading a spectrum using a one-cycle spreading code for one information modulation symbol, a delay time longer than the time of one information modulation symbol (hereinafter referred to as "information modulation symbol time") is used. When a delayed wave having the following is received, the delayed wave cannot be distinguished from the next spread spectrum information modulation symbol. Therefore, this indistinguishable delayed wave becomes an interference wave, which leads to deterioration of reception characteristics.

On the other hand, in the above-mentioned conventional method, the spectrum is spread by using a part of the long-period PN code for one information modulation symbol, and the PN code is spread for the next information modulation symbol. Is used to spread the spectrum. Therefore, even when a delayed wave having a delay time equal to or longer than one information modulation symbol time exists, the spread code used for spreading the spectrum is different between the information modulation symbol and the next information modulation symbol. For this reason, it is possible to distinguish between the two, and there is a characteristic that the reception characteristics do not deteriorate.

[0007] Each base station has a long-period PN.
A pilot signal using the code as a spreading code is transmitted. FIG. 8 is a diagram showing the P between the base stations in the conventional system described above.
It is a figure showing the timing relation of N code. In this figure, for simplicity, only transmission signals of pilot channels transmitted from two base stations, base station A and base station B, are shown. In this figure, reference numeral 2 denotes the long-period spreading code described above. As shown in the figure, all base stations use the same spreading code 2, and use spreading codes 2 with timings (phases) shifted by time T, respectively. ing.

[0008] The mobile station receives the pilot signal,
The synchronization timing of the spread signal of the base station is detected from the signal, and the base station is identified using the offset time T of the signal. That is, when the timing (phase) of the reference sequence at the time of despreading differs by time T, it is determined that the signal is from a different base station.

FIG. 9 is a diagram showing a configuration example of a synchronization detection / despreading unit of a mobile station receiver in a conventional CDMA mobile communication system. In this figure, reference numeral 3 denotes a search receiving section for detecting synchronization. The search receiving section 3 includes a despreading PN generating section 4 for generating a despreading reference PN code, a received signal and the despreading PN generating section. multiplier for multiplying the the generated reference PN sequence in part 4 5 _1, 1 integrator 7 ₁ for integrating the output of multiplier 5 ₁ over information modulation symbol interval, and, in the correlation output from the integrator 7 ₁ It comprises a synchronization detection circuit 8 for detecting a peak position. Reference numeral 10 denotes a finger receiving unit, which is a despreading PN generating unit 6 for generating a reference PN code for despreading of the traffic channel in accordance with the synchronization timing information supplied from the synchronization detection circuit 8; and a integrator 7 ₂ for integrating the output of the multiplier 5 ₂ and the reference PN sequence generated in use PN generator 6 over multiplying multipliers 5 _2, 1 information modulation symbol interval. Further, reference numeral 9 denotes an output of the finger receiving unit 10, and 11 denotes an input of the synchronization detecting / despreading unit.

[0010] The synchronization detection and
In the despreading section, the received signal is input to the input 11 of the synchronization detection / despreading section. The input signal includes a search receiving unit 3 for detecting the timing of despreading of a pilot signal and a finger receiving unit 1 for demodulating a received signal of a traffic channel.
Input to 0. In the search receiver 3, for timing detection of the despread to generate while shifting the timing (phase) reference PN code of 2 ¹⁵ cycles in the inversely spreading PN generator 4. That is, the timing by the PN code and a received signal generated from the inversely spreading PN generator 4 is multiplied by the multiplier 5 ₁ integrates the integrator 7 ₁ The product result for one information modulation symbol interval To obtain the correlation value at. Next, the generation timing of the reference PN code in the despreading PN generation unit 4 is shifted by a predetermined amount,
The phase is multiplied reference PN code and the received signal offset to obtain the correlation value by integrating the integrator 7 ₁ over 1 information symbol interval. Hereinafter, a correlation waveform is obtained while sequentially shifting the generation timing of the reference PN code (sliding correlation processing).

FIG. 10 is a diagram showing an example of a correlation waveform as a result of multiplying the received signal by the reference PN code. 10, the horizontal axis represents the phase of the reference PN sequence is generated in the PN generator 4 for the despreading, and the vertical axis represents the correlation value output from the integrator 7 ₁ in each phase. In this figure, reference numeral 12 denotes a correlation waveform resulting from the product of the received signal and the reference PN code, and reference numeral 13 denotes a peak point of the correlation waveform. At the point where the timing of the PN code of the received signal coincides with the timing of the reference PN code (synchronization point), the magnitude of the correlation waveform has a peak 13. The synchronization detection circuit 8 observes the correlation waveform, and detects the synchronization timing between the received signal and the despreading PN code from the timing information of the PN code generated by the despreading PN generating unit 4.

In finger receiving section 10, despreading P
The N generator 6 generates a reference PN code for demodulation according to the synchronization timing detected by the synchronization detection circuit 8. The reference PN code and the received signal is multiplied by the multiplier 5 _2, multiplication product result is 1 information modulation symbol integrated in the integrator 7 _2. As a result, a correlation waveform of the traffic channel is obtained at the output 9, and this correlation waveform is not shown in the RA (not shown).
It is sent to a KE combining unit and a demodulating unit to perform RAKE combining and demodulation.

[0013]

As described above, in the conventional method, a method of detecting a synchronization timing using a sliding correlation is adopted. However, this method uses a reference PN code shifted in timing (phase). Generate and multiply with the received signal, further integrate one information modulation symbol section to obtain a correlation waveform, and obtain a synchronization timing from the timing (phase) of the reference PN code at the peak point of the obtained correlation waveform. Therefore, the time required to obtain the synchronization timing is (integration time of one information modulation symbol) × (the number of times the timing (phase) of the reference PN code is shifted until the synchronization timing is obtained). The worst value of the number of times of shifting the timing (phase) is the number of periods of the PN code, and there is a problem that it takes a long time for synchronization detection.

Further, in the above-described conventional method, the information modulation symbol is spread and despread by using a part of the long-period PN code as the spread code and the reference PN code. Is
The partial correlation of the long-period PN code used for spreading the spectrum is obtained. M having a sequence length of 2 ⁿ -1 as a spreading code
When a sequence is used, in one-cycle autocorrelation, the peak value of the correlation is a value (2 ⁿ -1) corresponding to the processing gain, and the absolute value of the other correlation is 1. On the other hand, in the case of the conventional method using the partial correlation of the PN code, as shown in FIG.
It is known that the absolute value of the correlation other than 3 takes a value larger than 1. Therefore, in the CDMA mobile communication system described above, the ratio between the peak value of the correlation waveform and the other correlation values, that is, (absolute value of the peak of the correlation waveform) / (absolute value of the correlation other than the peak point). Becomes smaller than the value of the processing gain.

On the other hand, when an M sequence is used as a spreading code and one cycle of the spreading code is assigned to one information modulation symbol, obtaining a correlation waveform on the receiving side requires one of the M sequences.
Since this is equivalent to taking the autocorrelation of the period, (absolute value of the correlation peak between the spreading code and the reference PN code) / (absolute value of the correlation other than the peak point) is a value corresponding to the processing gain.
Therefore, in the conventional method, the ratio between the peak of the correlation waveform and the size of the other points is smaller in the conventional method than in the method of performing the spread spectrum of one information modulation symbol using one cycle of the M sequence. The ratio between this peak and the other points affects the accuracy of the synchronization timing detection, and there is a problem that the accuracy of the synchronization timing detection deteriorates when the value of the ratio decreases.

As described above, in the above-mentioned conventional CDMA mobile communication system, the spectrum is spread by using a part of one long-period PN code.
In comparison with the method of assigning one spreading code to one information modulation symbol, there is a problem that the ratio between the peak of the correlation waveform and other values becomes smaller, and the synchronization detection characteristic deteriorates. Furthermore, since a reference PN code is generated with its timing (phase) shifted sequentially and a sliding correlator for obtaining a correlation value over one information modulation symbol is used, there is a problem that it takes time to detect synchronization.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a CDMA mobile communication system and a CDMA transmitting / receiving apparatus which can reduce the time required for synchronization detection and prevent deterioration of synchronization detection characteristics.

[0018]

In order to achieve the above object, a CDMA mobile communication system according to the present invention comprises:
A CDMA mobile communication system having a transmitting device and a receiving device, wherein the CDMA transmitting device, when a is an arbitrary integer, a + 1st information modulation symbol on the transmitting side.
.., And the (a + N) th symbol are spread using the first, second,..., Nth spreading codes (N is an integer of 2 or more). And the CDMA receiving apparatus is configured to
N matched codes respectively corresponding to the Nth spreading code
A filter, a delay circuit provided corresponding to each of the matched filters, for delaying the output of the corresponding matched filter by 0 to (N−1) information modulation symbol times, the respective matched filters and the respective A synchronization detecting section for detecting the synchronization timing of the spread code from the output of the delay circuit.

Further, the CDMA transmitting apparatus of the present invention, when a is an arbitrary integer, the first, the (a + 2) th,... It has a function of performing spectrum spreading using the second,..., N-th spreading codes (N is an integer of 2 or more). Further, the CDMA receiving apparatus of the present invention is provided with N matched filters respectively corresponding to the first to N-th spreading codes (N is an integer of 2 or more), and provided for each of the matched filters, A delay circuit for delaying the output of the corresponding matched filter by 0 to (N-1) information modulation symbol times, and a synchronization for detecting a synchronization timing of the spread code from the outputs of the matched filters and the delay circuits. And a detection unit.

In the CDMA mobile communication system of the present invention, one cycle of a spreading code is assigned to one information modulation symbol. Values other than the peak point of the correlation waveform can be made closer to 1. Therefore, (absolute value of the peak of the correlation between the spreading code and the reference PN code) / (absolute value of the correlation other than the peak point) can be made close to the processing gain, and the characteristic deterioration at the time of synchronization detection can be prevented. . In addition, since the number of matched filters corresponding to each spreading code is used for synchronization detection and the synchronization is detected using the result of delaying the output, the synchronization time can be significantly reduced compared to the conventional method. Becomes

[0021]

FIG. 1 is a diagram showing the timing of a spreading code in an embodiment of a CDMA mobile communication system according to the present invention. In this figure describes a case of using a sequence of period 2 ⁷ -1 = 127 as the spreading code as an example. In the figure, 14 is the first information modulation symbol, 15 is the second information modulation symbol, 16 is the Nth information modulation symbol, and 17 is the N + th information modulation symbol.
Indicates the first information modulation symbol. In addition, 18 is the first
The 19th spreading code, 19 is the second spreading code, and 20 is the Nth spreading code. Here, N is an integer of 2 or more.

In the spread spectrum unit of the CDMA mobile communication system according to the present invention, the first information modulation symbol 14
Is multiplied with the first spreading code 18, the second information modulation symbol 15 is multiplied by the second spreading code 19, and the Nth information modulation symbol 16 is multiplied by the Nth spreading code 20. To spread the spectrum. Further, the N + 1-th information modulation symbol 17 is multiplied by the first spreading code 18 to spread the spectrum. Similarly, for the (N + 2) to 2N-th information modulation symbols, The spread of the spectrum is performed by using the second to Nth spreading codes and sequentially using the first to Nth spreading codes in the same manner. As a result, even if there is a delayed wave having a delay time equal to or longer than one information modulation symbol time, if the delay time is equal to or less than N information modulation symbol times, the spectrum of the information modulation symbol and the next information modulation symbol will be different. The spreading code used for spreading is different. Therefore, as in the case of the conventional method, it is possible to identify a delayed wave having a delay time equal to or longer than one information modulation symbol and the next information modulation symbol.

FIG. 2 shows an example of code timing between base stations in the embodiment of the present invention. FIG. 2 shows the timing of the spreading code used by base stations A and B to spread the spectrum of the information modulation symbol.
Are the first of the spread codes at the time of the first, second,.
, No. 2,..., Nth spreading code. Also,
In the base station B, the first and second information modulation symbols,
.., The Nth, the second,..., The first, and the like, the order of the spreading codes used for other base stations is changed. As described above, pilot signals from different base stations use P
Since the order of the N codes is different, if the order of the PN codes of the pilot signal of the base station is known in the mobile station, it is possible to identify each base station using the difference in the order. When N spreading code sequences are used,
N! Base stations can be identified.

As described above, in the present invention, since one spreading code is assigned to one information modulation symbol, a combination having a small cross-correlation value of the spreading code can be used. As described above, the correlation value other than the peak point of the correlation waveform does not increase due to the partial correlation.

FIG. 3 shows a configuration example of the despreading / synchronization detecting section of the receiving apparatus in the CDMA mobile communication system of the present invention. In this figure, reference numerals 22, 23, and 24 denote matched filters for the first, second, and Nth spreading codes, respectively, and 25 delays the correlation waveform of the matched filter output by one information modulation symbol time. This is a delay circuit that causes the delay. Reference numeral 26 denotes a synchronization detection circuit that identifies a base station and detects synchronization. These constitute a search receiving section 212 in the receiving apparatus of the present invention.

As shown, each matched filter 2
N-1 delay circuits 25 are connected in series to 2 to 24, respectively. Accordingly, reference numeral 27 denotes an output signal (correlation waveform) of the matched filter 22 for the first spreading code, and reference numeral 28 denotes an output 27 of the matched filter 22 (N
-2) signal delayed by information modulation symbol time, 29
Is a signal obtained by delaying the output 27 of the matched filter 22 by the (N-1) information modulation symbol time. Similarly, 30, 31, and 32 denote the output signal (correlation waveform) of the matched filter 23 and the output 30 of the matched filter 23 for the second spreading code, respectively, as (N-2).
A signal delayed by the information modulation symbol time and a signal obtained by delaying the output 30 of the matched filter 23 by (N-1) information modulation symbol time. In addition, 3
Reference numerals 3, 34 and 35 denote an output signal (correlation waveform) of the matched filter 24 for the N-th spreading code, a signal obtained by delaying the output 33 of the matched filter 24 by (N-2) information modulation symbol time, And a signal obtained by delaying the output 33 of the matched filter 24 by (N-1) information modulation symbol time. Reference numeral 36 denotes a finger receiving unit, 37 denotes a PN code generator for despreading the traffic channel signal, 5 denotes a multiplier, and 7 denotes an integrator.

The operation of the despreading / synchronization detecting section in the receiving apparatus of the present invention thus configured will be described. Here, the matched filters 22, 2 at a certain time t
The output waveforms 27, 30, 33 of 3, 24 are respectively represented by f ₁
(T), f ₂ (t), f _N (t), 27, 30,
Waveforms 28, 31, and 34 obtained by delaying 33 by (N−2) information modulation symbols have f ₁ (t− (N−2) T _s ) and f ₂
(T− (N−2) T _s ) and f _N (t− (N−2) T _s ), and the waveforms 29, 32, 27, 30, 33 are delayed by (N−1) information modulation symbol time. 35 is f ₁ (t− (N
_{-1) T s), f 2} (t- (N-1) T s), f N (t-
The _{(N-1) T s)} . Here, T _s is the time of one information modulation symbol.

Here, it is assumed that the base station A has transmitted a pilot signal that has been spread in spectrum in the order of the spreading code shown in FIG. That is, the first information modulation symbol has the first spreading code, the second information modulation symbol has the second spreading code, and the Nth information modulation symbol has the Nth spreading code. It is assumed that a pilot signal whose spectrum has been spread using the above is transmitted.

FIG. 4 shows the waveforms of the matched filters 22 to 24 and the outputs 27 to 35 of the respective delay circuits 25 when the reception of the N-th information modulation symbol of the signal from the base station A is completed. It is a figure showing an example of.
As can be seen from this figure, when the reception of the N-th information modulation symbol is completed, the first information modulation symbol spectrum-spread with the first spreading code is temporally (N−1). Since the signal is received before the information modulation symbol time, the autocorrelation waveform appears at the output 29 obtained by delaying the output 27 of the matched filter 22 matched to the first spreading code by (N-1) information modulation symbols. At this time, the other waveform outputs 32 and 35 having the same delay time have only noise components because the respective matched filters 23 and 24 do not match the spreading code.

The second information modulation symbol received at the next time point, that is, before the (N-2) information modulation symbol time, has its spectrum spread with the second spreading code. An autocorrelation waveform is obtained only at an output 31 which is a result of delaying the output 30 of the matched filter 23 matched with the spreading code by the (N-2) information modulation symbol time, and the output 30 is not matched with the spreading code. The waveforms 28 and 34 obtained by delaying the output of the matched filter in (N-2) by the information modulation symbol have only noise components.
Similarly, in the N-th information modulation symbol received last, a correlation waveform is obtained only at the output 33 of the matched matched filter, and the other waveforms 27 and 30 become noise components. Note that the absolute values of the peak points of the waveforms 29, 31, and 33 are values corresponding to the processing gains, and the absolute values of the points other than the peak points are obtained by the cross-correlation with the spreading codes used for spreading the information modulation symbols before and after the peak points. This is a value larger than 1. However, in the present invention, the value of the correlation waveform other than the peak point can be changed by selecting a combination of the first to Nth spreading codes used for spreading the information modulation symbol.

In the synchronization detecting circuit 26, it is assumed that the information of the spreading codes used by each base station and the order of the spreading codes are known.
Therefore, the synchronization detection circuit 26 outputs the outputs 27 to 3
5 for all combinations of the input signals from the base station, determine whether the received signal is noise or a correlation waveform, and check the spreading code used by each base station with the information on the order, so that the signal from which base station is received. Identify In this example, the synchronization timing is detected by detecting the position of the peak point from the correlation waveforms of 29, 31, and 33. In the synchronization detection circuit 26, (1) from which base station a signal is received, (2) a spreading code used by the receiving base station and its order, and (3) information on synchronization timing. The three pieces of information are sent to the PN code generator 37 of the finger receiver 36.

In the PN code generator 37, 26
A reference PN code for demodulation is generated based on the information obtained from, and the spectrum is despread using the multiplier 5 and the integrator 7. Demodulation of a traffic channel and RAKE reception are performed using the result of the despreading.

As described above, according to the present invention, the base station can be identified simultaneously with the synchronization detection. And
Since a matched filter is used in the present invention, (1)
Synchronization can be detected in a short time of (information modulation symbol time) × (total of delay times by delay circuits). Further, in the conventional method, a long-period PN code is divided and used, and when this long-period PN code is selected, (absolute value of the peak of the correlation waveform) / (correlation of the correlation other than the peak point). (Absolute value) was determined to be smaller than the processing gain. On the other hand, in the present invention, since a combination of a plurality of PN codes is used for spreading the spectrum, the combination of the PN codes can be selected. Therefore, P such that the value of the cross-correlation decreases with respect to each other
If the N code is selected, the value of (absolute value of the peak of the correlation waveform) / (absolute value of the correlation other than the peak point) can be made close to the value of the processing gain, thereby preventing the characteristic deterioration at the time of synchronization detection. Can be.

In the present embodiment, the reference PN code for demodulation is generated by the PN code generator 37 based on the information detected by the synchronization detector 26, and the spectrum is despread. , 27 to 35 can be used as they are to perform demodulation of a traffic channel and RAKE reception. In this case, the same effect can be obtained.

Next, another embodiment of the present invention will be described. Also in this embodiment, the timings of the spread spectrum on the transmitting side and the configuration of the despreading / synchronization detecting section use those shown in FIGS. 1 and 3. Here, for simplicity of explanation, the base station is shown in FIG.
The case where only the base stations A and B shown in FIG. As shown in FIG. 2, in the base station A, the first, second,..., Nth information modulation symbols are the first, second,. , N-th, and the base station B assigns the first, second,..., N-th information modulation symbols to the N-th, second,. , The first spreading code is assigned in a different order from that of the base station A.

In this embodiment, since the order of the spreading codes received by the synchronization detecting circuit 26 is known in advance, the matched filter is used so as to correspond to the order of the spreading codes of the base station A by using the information. And the outputs of the delay circuits are combined to form f ₁ (t− (N−1) T _s ) + f ₂ (t−
(N−2) T _s ) +... + F _N (t) is obtained, and the base station B is determined.
, The outputs of the matched filter and the delay circuit corresponding to the order of the spreading codes used in the base station B are combined to obtain f _N (t− (N−1) T _s ) + f ₂ ( t-
(N−2) T _s ) +... + F ₁ (t).

FIG. 5 is a diagram showing an example of the configuration of the synchronization detecting circuit 26 in this embodiment. As shown in the figure, the synchronization detecting circuit 26 in the present embodiment is provided with adding means 40 and 41 to which correlation waveforms in the order corresponding to each base station are input. That is, the adding means 40 is an adding means provided corresponding to the base station A, and as shown in the figure, an input corresponding to the order of spread signals of the base station A, that is, f ₁ (t− (N− 1) T _s ), f ₂
(T- (N-2) T s), ..., the corresponding input 29, 31 respectively to _{f N (t), ...,} 33 are connected. Therefore, from the output 38 of the adding means 40, f ₁ (t
− (N−1) T _s ) + f ₂ (t− (N−2) T _s ) +.
+ F _N (t) is synthesized and output.

The addition means 41 is provided corresponding to the base station B, and as shown in FIG.
, F _N (t− (N−1) T _s ), f
Inputs 35,..., 31, 27 corresponding to ₂ (t− (N−2) T _s ),..., F ₁ (t) are connected. As a result, f _N (t− (N−
1) T _s ) + f ₂ (t− (N−2) T _s ) +... + F
₁ (t) is synthesized and output.

When a signal from base station A is being received,
Output 27 of delay circuit connected to matched filter
Since 35 is as shown in FIG. 4, f ₁ (t−
_{(N-1) T s)} + f 2 (t- (N-2) T s) + ···
+ F _N (t) result 38 and f _N (t− (N−1)
T _s ) + f ₂ (t− (N−2) T _s ) + f ₁ (t) Result 3
9 is as shown in FIGS. 6 (a) and 6 (b). As can be seen from this figure, a waveform having a sharp peak is obtained as a result of combining the input signals corresponding to the receiving base station A as shown in FIG. On the other hand, the synthesis result corresponding to the other base stations has a noise component synthesized,
A waveform having a sharp peak as shown in (b) cannot be obtained. By utilizing this property, it is possible to determine the base station from which the signal is being received, and to obtain the timing (phase) of the peak, thereby obtaining the synchronization timing. Other operations are the same as those of the first embodiment.

As described above, according to this embodiment, the synchronization detecting circuit 26 only needs to determine whether the output from the adding means provided for the base station is a noise or a correlation waveform. Become. In addition, it is possible to use a matrix switch for switching the input to each adding means so as to be able to respond to the change of the base station to be received.

In the above description, the case of base station transmission and mobile station reception has been described.
The same applies to the case of base station reception.

[0042]

As described above, the CDM of the present invention constructed as described above
According to the mobile communication system A, since one spreading code is assigned to one information modulation symbol, selecting the spreading code prevents the correlation value other than the peak point of the correlation waveform from increasing. And the deterioration of the synchronization characteristics can be prevented. In addition, since a matched filter is used, synchronization can be detected by (1 information modulation symbol time) × (total delay time by a delay circuit).
The synchronization detection time can be greatly reduced as compared with the conventional method.

[Brief description of the drawings]

FIG. 1 is a diagram showing the timing of spread spectrum in one embodiment of the present invention.

FIG. 2 is a diagram for explaining a method of identifying a base station according to one embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration example of a despreading / synchronization detecting unit of the receiving device according to the embodiment of the present invention.

FIG. 4 is a diagram showing an example of a correlation waveform output from a matched filter and a delay circuit.

FIG. 5 is a diagram illustrating a configuration example of a synchronization detection circuit 26 according to another embodiment of the present invention.

FIG. 6 is a diagram for explaining an operation in another embodiment of the present invention.

FIG. 7 is a diagram showing the timing of spread spectrum in the conventional method.

FIG. 8 is a diagram for explaining a conventional method for identifying a base station.

FIG. 9 is a diagram illustrating a configuration example of a despreading / synchronization detecting unit of a conventional mobile station.

FIG. 10 is a diagram illustrating an example of a correlation waveform output of a received signal and a reference PN code.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 information modulation symbol 2 spreading PN code 3 search receiving unit 4 despreading PN generating unit 5, 5 ₁ , 5 ₂ multiplier 6 despreading PN generating unit 7, 7 ₁ , 7 ₂ integrator 8 synchronization detection circuit 9 Finger receiver output 10 Finger receiver 11 Sync detection / despreader input 12 Correlation waveform 13 Peak point of correlation waveform 14 1st information modulation symbol 15 2nd information modulation symbol 16 Nth information modulation symbol 17 N + 1st Information modulation symbol 18 1st spreading code 19 2nd spreading code 20 Nth spreading code 21 Search receiving section in embodiment of the present invention 22 Matched filter for 1st spreading code 23 2nd 24 Matched filter for Nth spreading code 25 Delay circuit for one information modulation symbol time 26 Output of synchronization detection circuit 27 22 Output signal of signal 22 22 delayed by one information modulation symbol 29 Signal of output 22 22 delayed by N information symbols 30 Output of signal 23 Signal of output of 23 delayed by 1 information modulation symbol 32 The signal obtained by delaying the output of 23 by N information modulation symbol time 33 33 The output of 34 24 The signal obtained by delaying the output of 24 by one information modulation symbol time 35 The signal obtained by delaying the output of 25 25 by N information modulation symbol time 36 One embodiment of the present invention Finger receiving section 37 of the embodiment 37 PN generating section for despreading 38 f _N (t− (N−1) T _s ) + f ₂ (t− (N−)
2) Waveform of T _s ) + f ₁ (t) 39 f ₁ (t− (N−1) T _s ) + f ₂ (t− (N−
2) T _s ) + f _N (t) waveform 40, 41 Addition means

Claims (3)

[Claims] 1. A CDMA mobile communication system having a CDMA transmitting device and a receiving device, wherein the CDMA transmitting device has a
The (a + 1) th symbol of the information modulation symbol on the transmission side,
.., And the (a + N) th symbol has a function of performing spectrum spreading using first, second,..., Nth spreading codes (N is an integer of 2 or more). The CDMA receiving apparatus is provided with N matched filters respectively corresponding to the first to Nth spreading codes, and is provided for each of the matched filters, and outputs an output of each of the matched filters corresponding to 0. (N-1) a delay circuit for delaying the information modulation symbol time, and a synchronization detection unit for detecting the synchronization timing of the spread code from the outputs of the matched filters and the delay circuits. CDMA mobile communication system. 2. When a is an arbitrary integer, the (a + 1) th symbol, the (a + 2) th symbol,
,..., The (a + N) th symbol, using a first, second,..., Nth spreading code (N is an integer of 2 or more) to perform spectrum spreading.
DMA transmitter. 3. N matched filters respectively corresponding to first to N-th spreading codes (N is an integer of 2 or more), and the matched filters provided corresponding to the respective matched filters.・ Set the filter output to 0
(N-1) A CDMA receiver comprising: a delay circuit for delaying an information modulation symbol time; and a synchronization detection unit for detecting a synchronization timing of the spread code from an output of each of the matched filters and each of the delay circuits. apparatus.